Effects of atrazine, chlorpyrifos, and their interactions on anti-predator behavior and activity in African clawed frogs, Xenopus laevis

Abstract

Two separate experiments were conducted to examine potential mixture effects of chronic, sub-lethal concentrations of atrazine and chlorpyrifos on the alarm response and activity of larva of the African clawed frog, Xenopus Laevis. Larvae were exposed to three concentrations of atrazine, (0, 20, and 200 μg/L), three concentrations of chlorpyrifos (0, 1, and 10 μg/L), and all possible combinations of those doses for a period of two weeks prior to behavioral testing. Activity of larvae was evaluated by measuring both how many seconds the larvae spent active in any way and also by measuring the number of times the larvae crossed the center line of their experimental container. Alarm responses were provoked by introduction of an “alarm substance,” to which larvae reacted by exhibiting anti-predator behavior. This alarm response was evaluated by measuring the amount of time spent active before and after alarm substance introduction (depressed activity is the typical alarm response), as well as the amount of time spent opposite the end of the experimental container where the alarm substance was introduced. Behavioral trials were videotaped for purposes of data collection.